Intraocular-external lens combination system and method of using same

ABSTRACT

An intraocular lens system including a lens having a negative-powered section for use in combination with a positive-powered external lens system. The intraocular lens is preferably positioned in the posterior chamber of the eye and is configured so as to provide maximum separation between the intraocular lens and the external lens system, thereby achieving maximum magnification and field of view. Alternatively, the refracting powers of the lens system can be reversed, thus resulting in image demagnification.

This application is a continuation of application Ser. No. 07/687,190,filed Apr. 18, 1991, now abandoned, which is a continuation ofapplication Ser. No. 07/432,852, filed Nov. 7, 1989, now U.S. Pat. No.5,074,875, which is a continuation of application Ser. No. 07/289,459,filed Dec. 22, 1988, now abandoned, which is a continuation ofapplication Ser. No. 07/218,820, filed Jul. 12, 1988, now abandoned,which is a continuation of application Ser. No. 07/109,165, filed Oct.16, 1987, now abandoned, which is a continuation of application Ser. No.06/316,920 filed Oct. 30, 1981, which is now U.S. Pat. No. 4,710,197,issued Dec. 10, 1987.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an intraocular lens for use in combination withan external lens system to form an image on the retina.

2. General State of the Art

One of the leading causes of blindness in America is maculardegeneration. In this condition, the central retina, which perceivesfine detail, is deficient. In the less severe cases of this disease,patients can often be helped by simple magnifiers or by varioustelescopes, both of which serve to enlarge the image formed on theretina.

Magnifiers are used for reading or other tasks involving near vision. Avariety of magnifiers are available and are generally useful for theirintended purpose. However, such magnifiers are bulky and inconvenientand are of no help in other tasks such as walking about. Such magnifiersare likewise tiring to the user, thus detracting from their usefulness.

For improved distant vision, a telescope is required. In order to besuitable for low vision patients, telescopes must be compact, lightweight, and reasonably inexpensive. These requirements together withbasic optical limitations generally result in a device which magnifiesbut with an enormous loss of visual field. For the low vision patient,with his natural lens, telescopes of 2.2×, 2.5×, or 3× are oftenprescribed for use outdoors, or for other distance viewing. The fieldloss is so great that most patients with macular degeneration do notfind telescopes of much practical value. Such telescopes are, therefore,often of limited practical use because of their narrow field, poorcosmetic appearance and difficulty in fitting to the patient's face. Asa result, they are used relatively infrequently by patients.

When patients have cataracts in addition to macular degeneration, theprognosis is even worse. Removal of the cataract, followed by visioncorrection with spectacles or contact lenses, renders the field ofvision smaller without significantly improving magnification.

The aphakic patient with a normal retina faces a formidable opticalproblem. Spectacle lenses of +11 to +16 diopters are needed to providethe required additional focusing power. The lenses are thick and must beprecisely fitted to the patient's face. Furthermore, the field of viewis restricted by the size and the refracting effect of the lenses.Alternatively, contact lenses of similar power may be worn. However, asubstantial number of patients, particularly older patients with limitedfinger dexterity, cannot wear contact lenses.

If the aphakic patient further has macular degeneration, theconventional telescopic low-vision aids mounted on the spectacle framewill be a problem. The telescope adds weight, and projects beyond thealready large spectacle lenses. The telescope further limits the fieldof vision. The field problem is aggravated by the fact that the presenceof the spectacle lens moves the telescope yet further from the eye thanthe optimum position.

Some aphakic low-vision patients can use a 6× or 8× hand-held telescope.The 6× has a field of view of 11°, while the 8× has a field of 8°. Yet,this solution is not viable for the many patients who do not have thesteadiness of hand to use such hand-held telescopes.

As a result of the above optical problems and the already reduced visualacuity, low-vision patients who develop cataracts are often not operatedon.

Conversely, in other instances demagnification of the optical image isdesirable. Thus, patients with retinitus pigmentosa (RP) and somepatients with advanced glaucoma suffer a loss of peripheral vision. Inorder to function normally, e.g., to cross the street, they may benefitfrom a visual aid that demagnifies the retinal image, thus putting moreof the visual field onto the central portion of the retina that is stillfunctional.

The principle of the invention and the various embodiments disclosedherein overcome the above deficiencies while achieving the objectivesset forth.

A search of the prior art has uncovered the following materials:

TROUTMAN, in an article entitled "Artiphakia and Aniseikonia", whichappeared in the American Journal of Ophthalmology, pages 602-639,October 1963, discusses the state of the art in artificial intraocularlenses. On page 614, the article states: "There is no reference in theliterature on intra-ocular lenses as to the telescopic magnificationwhich can be attained with the combination of an intraocular lens and aspectacle lens."

LEVY, Jr. et al., U.S. Pat. No. 4,074,368, disclose an intraocular lensthat is based on the principle of a Galilean telescope wherein both thenegative element 18 and the positive element 14 are fastened together,and both placed within the eye. Positive element 14 is an air lensformed by bubble 15, and negative element 18 is an air lens formed bybubbles 20 and 22. The patent suggests implantation of this intraocularlens system for relief of conditions such as macular degeneration anddiabetic retinopathy.

LIEB, U.S. Pat. No. 2,834,023, discloses anterior chamber lenses forrefractive correction of aphakia, high ametropia, and anisometropia, andbilateral and unilateral cataracts. Of particular interest are FIGS.6-9, wherein lens 20 is of the diverging type.

FILDERMAN, U.S. Pat. No. 3,027,803, discloses a spectacle lens-contactlens system which forms a modified Galilean telescope. Contact lens 10serves as the negative lens in the telescope lens system, and centralsegment L2 of spectacle lens L1 serves as the positive objective lens ofthe telescopic lens system. Furthermore, the patent discloses how a 2×magnification system can be developed by using a negative lens of -50diopters and a positive lens of +25 diopters.

DITTMER, U.S. Pat. No. 2,164,801, discloses a corrective lens systemwherein an alternate embodiment provides a telescopic lens system, asillustrated in FIG. 5. The telescopic lens system comprises negativecontact lens 23 which is worn on eye 10, and positive spectacle lens 24which is mounted in front of eye 10.

SPERO, U.S. Pat. No. 2,078,590, discloses telescopic spectacles whereinpositive lens 15 is secured to glass carrier member 16, and negativelens 17 is secured to second glass member 18. The total lens system issecured to a spectacle lens mounting system.

ISEN, in "Feinbloom Mini-Scope Contact Lens" as reported in theEncyclopedia of Contact Lens Practice (Nov. 15, 1961), teaches making aGalilean lens system out of a doublet constructed contact lens. As canbe seen, the negative lens is placed closest to the eye, while thepositive objective lens is placed a small distance away from the eye.

SUMMARY OF THE INVENTION

It is an object of the invention to overcome the above disadvantagesassociated with conventional devices and techniques, and to provide asystem allowing for improved vision with a greater field of vision thanwas previously possible.

It is a further object of the invention to provide an optical systemwhich is useful for improving distant vision by patients having maculardegeneration and aphakic patients and which is more acceptablecosmetically than are the presently available telescopic spectacles.

It is yet a further object of the invention to provide a systemproviding a demagnified retinal image thereby placing more of the visualfield onto the central portion of the retina thus aiding patientssuffering from loss of peripheral vision.

According to one embodiment of the invention, a negative-powerintraocular lens is provided which is adapted to be positioned in theposterior chamber of the eye. The intraocular lens is configured so asto provide an enlarged retinal image and a large field of vision whenused in combination with an exterior positive lens.

According to one preferred embodiment of the invention, the exteriorlens is a spectacle lens, while in another embodiment the external lensis a positive contact lens.

A second external lens may also be provided. In this instance, the firstexternal lens is a positive spectacle lens and the second external lensis a negative or a positive contact lens.

According to the invention, a method for providing improvedmagnification to human eyes having no natural lens is disclosed. Themethod comprises implanting a negative intraocular lens within the eye;and providing an external positive lens. A second external lens may beused, in which case the first external lens is a positive spectaclelens, and the second external lens is a negative or a positive contactlens.

According to a second aspect of the invention, the intraocular lens hasa positive power while the external lens has a negative power. Such acombination provides a system which demagnifies the image to the retinawhile providing an improved field of vision. Once again, the externallens can be a lens system comprising two lenses; i.e., a spectacle andcontact lens.

In the corresponding method, a positive IOL is implanted in an eye andis combined with an external negative lens so as to provide ademagnified image on the retina with an increased field of vision.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of an optical systemof the invention;

FIGS. 2A and 2B are front and side magnified cross-sectional views ofthe negative intraocular lens shown in FIG. 1;

FIGS. 3A and 3B illustrate cross-sectional views of the intraocular lensinserted in the posterior chamber;

FIG. 4 is a graph comparing the magnification and field of vision ofvarious optical systems, including the system of the invention;

FIG. 5 is a graph used for selecting the correct intraocular lens,depending upon the magnification desired;

FIG. 6 is a diagram illustrating the field of view obtained through aspectacle lens.

FIG. 7 is an alternative embodiment to the embodiment shown in FIG. 1for demagnifying the visual image.

FIG. 8 illustrates a negative intraocular lens positioned in theposterior chamber in combination with a positive contact lens;

FIG. 9 illustrates a negative intraocular lens positioned in theposterior chamber in combination with an external fresnel lens;

FIG. 10 illustrates a negative intraocular lens positioned in theposterior chamber in combination with a negative contact lens and apositive external spectacle lens;

FIG. 11 illustrates a positive intraocular lens in the posterior chamberin combination with a negative contact lens; and

FIG. 12 illustrates a negative intraocular lens positioned in theanterior chamber in combination with a positive external spectacle lens.

DESCRIPTION OF PREFERRED EMBODIMENTS

As was noted above, most broadly, the optical system of the inventionincludes an intraocular lens, such as is illustrated in FIGS. 1 and 2(or FIG. 7). Referring to FIG. 1, the negative power of the intraocularlens is selected such that, when a spectacle lens or contact lens ofappropriate power is worn, the patient will have a magnified retinalimage.

As was noted previously, the intraocular lens may be used in combinationwith either a contact lens and/or a spectacle lens. When combined with aspectacle or contact lens of a positive power, the combination willbehave as a Galilean telescope with a magnification factor greater thanunity.

As seen from FIG. 1, a spectacle lens 7 having a positive refractingpower is worn in combination with the negative intraocular lens 9 so asto focus the image on the retina 11. The intraocular lens is positionedbehind the iris. It is also possible, although far less preferable, toposition the lens in the anterior portion of the eye, between the corneaand the iris (FIG. 12).

It is an advantage of the invention that the intraocular lens ispositioned close to the pupil of the eye, thereby permitting the lens tobe of relatively small size, as compared, for example, withnegative-power contact or spectacle lenses which might otherwise be usedfor the same purpose. Additionally, by positioning the lens in theposterior chamber, maximum separation is achieved between the spectacleor contact lens used and the intraocular lens, thereby achieving maximummagnification.

The distance, v, shown in FIG. 1 is the vertex distance, defined as theseparation between the vertex of the cornea and the vertex of thespectacle lens. As will be explained below, this distance is importantin determining the magnification that is achieved.

The general intraocular lens structure contemplated is of the type whichis generally known, such as, for example, the type disclosed in U.S.Pat. No. 4,041,552 to GANIAS, the disclosure of which is herebyincorporated by reference.

As may be seen from FIGS. 2A and 2B, the intraocular lens is providedwith loops or haptics 13 of plastic or metal for holding the lenselement 15 firmly in position. FIG. 2B illustrates relative dimensionsin millimeters. The clear aperture (CA) in this example is 4.5 mm.

FIG. 3A shows one possible technique for positioning the lens in theposterior chamber of the eye. As illustrated, the haptics 13 expand byspring tension, contacting the inside surface of the capsule 15. In FIG.3B, the situation is illustrated in which the capsule has been removed,as in an intracapsular extraction. In this case the loops 13 expandagainst the ciliary body 17 and thereby position the IOL. The loops areshown as being inclined with respect to the plane of the IOL, thepurpose being to position the IOL in a posterior position thus providingadded separation between the IOL and the exterior lens. The decision asto the type of IOL to use may be made at the time of surgery.

Naturally, in this embodiment, the intraocular lens and the spectacleand/or contact lens must be appropriately selected so as to provide thedesired degree of magnification, and a sharply focused retinal image,while providing optimal field of vision.

The power, P, of the IOL can be calculated from the equation: ##EQU1##where n=index of refraction of the intraocular media=1.336

g=distance from cornea vertex to the retina (FIG. 1) in meters (m).

b=distance from cornea vertex to the IOL (m)

v=vertex distance of spectacle lens (m)

C=power of cornea, in diopters

F=focal length of normal (phakic) eye

M=magnification desired

Once the power of the IOL has been determined from Equation 1, thepower, S, of the spectacle lens can be found as follows: ##EQU2##

S is the power required for distant vision. If correction is needed fornear vision, appropriate additional power can be added to S.

The field of view is defined with the help of FIG. 6. The total angularfield is defined as the angle α. ##EQU3## where d=diameter of spectaclelens (m)

v=vertex distance from spectacle lens to the cornea (m)

k=distance from cornea vertex to nodal point of the eye (m). For thenormal eye k=0.007 m.

S=power of spectacle lens, in diopters.

Practically speaking, the procedure for selection of the appropriatelenses may be as follows. The patient's requirements for magnificationand field of view are determined from a detailed examination, includingvisual acuity, if possible, and from determination of the patient'svisual needs, e.g., distance vision vs. reading. From the availablenegative IOLs, the power that best meets the patient's requirements isselected. A graph such as that illustrated in FIG. 4 may be used forthis purpose. The intraocular lens will have a power of -10 to -100diopters with lenses of -40 diopters to -100 diopters being verysuitable. After the implant surgery, when the eye has stabilizedsufficiently, the patient is refracted to determine the best spectacle(or contact lens) for optimum vision.

The spectacle lens can be of the conventional glass or plastic type. Itis also possible to use a positive Fresnel lens in some cases (FIG. 9),in order to reduce the weight of the spectacle. These lenses consist ofthin plastic on which circular sections of a lens have been embossed.The finished piece acts as a lens, but the total thickness is much lessthan the conventional lens. They are especially useful in situationsrequiring large positive (or negative) dioptic powers.

FIG. 4 illustrates the magnification and field of view obtainable forthe various IOL powers indicated in parentheses. For purposes ofillustration, a fixed diameter of spectacle lens, 40 mm, was assumed. Ifa smaller diameter spectacle lens, or a spectacle lens that is not roundis used, the field will be different from that shown. Also illustratedin FIG. 4 are the magnification and field obtainable in a number ofcurrently available telescopic low vision aids, such as the Bioptic, andthe "Designs for Vision" Wide Angle Telescope. It is apparent that forany given magnification up to 2.5×, the combination of IOL plusspectacle lens yields a wider field of view than the conventionaltelescopic low vision aids.

Curve B in FIG. 4 illustrates the magnification and field obtainablewith the combination of a contact lens and a spectacle lens. Since it isimpractical to utilize contact lenses of extreme negative power, thecurve is extended only to -30 D. Curve B indicates that themagnification obtainable with this combination is quite limited.Comparison with curve A shows that for a given magnification, the fieldobtainable with the IOL/spectacle combination is superior to that of theCL/spectacle combination.

FIG. 5 is a graphical representation of the relation between IOL powerand magnification for various combinations of IOL and external lenses.Line A gives the magnification as a function of IOL power for thecombination of an IOL and a spectacle lens located at a vertex distanceof 13 mm (v=0.013 m) from the cornea. This vertex distance is typicalfor many patients. Each figure in parenthesis is the required power ofthe external lens, the spectacle lens in this case. Line B is for thecombination of an IOL together with a contact lens. It is apparent thatthis combination does not offer the degree of magnification that can beobtained with the IOL/spectacle combination. The reason is that the IOLand the CL are of necessity in fairly close proximity, as dictated bythe anatomy of the eye.

Line C is for the more complex combination of an IOL, a contact lens of-20 D power, and a spectacle lens. This arrangement increases themagnification available compared to either of the above combinations.The price to be paid for this additional magnification is theinconvenience of wearing a contact lens as well as a spectacle lens, andthe increased power necessary in the spectacle lens.

Line D represents the IOL/spectacle combination with a vertex distanceof 23 mm for the spectacle. For a spectacle lens diameter of 40 mm., anda 7 mm, distance between the cornea and nodal point of the eye, aspectacle lens power of 21.4 diopters will yield a field of view ofabout 26.84° using the above formula. Thus, fields of view of 27° orgreater are possible. This additional 10 mm of vertex distance is seento give a significant increase in magnification compared to line A.There are two implications to this observation. First, a givenmagnification can be achieved with a lower power IOL and lower powerspectacle lens if the vertex distance can be somewhat greater than thestandard 13 mm. Second, and perhaps more important, after an IOL hasbeen in place for a few years, the patient may require increasedmagnification, due to progressive macular degeneration. Rather than riska second operation to replace the IOL, the patient can be fitted withspectales having a greater vertex distance. For example, if the IOL werea -60 D lens, the initial magnification for a vertex distance of 13 mmwould be 1.97×. Later the magnification could be increased to 2.5×byincreasing the vertex distance to 23 mm, together with an appropriatechange in the power of the spectacle lens. While an increase in vertexdistance does create minor problems in fitting spectacle lenses and incosmetic appearance, the disadvantages are less objectionable than thetraditional telescopic spectacles or hand-held telescopes.

As seen from the information provided by the graphs, the system of theinvention provides improved magnification and increased field of visionover systems which are commonly available, while being easier to use andbeing far more cosmetically acceptable. As was noted previously, it is asignificant advantage of the invention that, for a given magnification,the intraocular lens-spectacle combination provides a larger field ofview than any of the alternatives shown in FIG. 4.

Additional advantages of the inventive combination are lighter weight,and fewer optical elements to be maintained in alignment. Cosmetically,a simple lens in front of the eye, even a strong positive lens, is lessobjectionable than a telescope mounted on the spectacle frame, as ispresently employed.

The advantages of a system providing a wide field of view are obvious. Awide field greatly increases the ability of the patient to move about,to avoid obstacles, and generally to function normally, and, therefore,provides a viable alternative to systems which have been proposedpreviously.

As has been noted above, the intraocular lens may be used in combinationwith a contact lens instead of a spectacle lens. The negativeintraocular lens and positive contact lens once again act to form aGalilean telescope. However, this embodiment is less preferred byvirture of the shorter spacing between the two lenses, as compared withthe spacing between the intraocular lens and a spectacle lens. Themagnification which is obtained is, therefore, quite limited and fixed,as a result of the anatomy of the eye.

In yet another embodiment of the invention (FIG. 10), a negative contactlens may be used in combination with a negative intraocular lens and apositive spectacle lens to satisfy the parameters set forth previously.However, by virtue of the extra problems associated with contact lenswear, as well as the additional problems of alignment of the threelenses, this system is likewise less preferable than the simpleintraocular lens - spectacle lens system.

An additional embodiment of the invention employs a positive contactlens in combination with a positive spectacle lens and a negativeintraocular lens. By dividing the required positive power between thespectacle lens and the contact lens, the power of the spectacle lens canbe reduced, thus reducing its weight and improving the cosmeticappearance. Furthermore, for a given magnification, the field of view issomewhat greater for the combination including the positive contact lensthan for the spectacle/IOL combination.

FIG. 7 illustrates an alternative embodiment of the invention which isuseful with patients suffering from reduced peripheral vision. In thisembodiment, the IOL and external lens powers are reversed such that theIOL 9' has a positive power while the external lens 7' has a negativepower. A graph similar to that shown in FIG. 5 may be used for selectingvarious lens powers after the patient's visual requirements have beenevaluated. By way of example, in this embodiment an IOL having a powerof 40 D in combination with a spectacle lens of -25 D power at a vertexdistance of 23 mm gives a magnification of 0.59 (i.e., a demagnificationof 41%).

Although the invention has been described with respect to particularmaterials, lenses, and intraocular lens systems, it is to be understoodthat the invention is not limited to the particulars disclosed, butextends to all equivalents falling within the scope of the claims.

We claim:
 1. A method for providing demagnification of an image on theretina of an eye of a patient while providing an increased field ofvision, said method comprising:a) evaluating visual requirements of thepatient to determine a combination of an intraocular lens comprising apositive section with an external negative lens to provide substantialdemagnification while providing an increased field of vision; b)implanting the intraocular lens comprising a positive section withinsaid eye; and c) providing the external negative lens.
 2. The method asdefined by claim 1 comprising implanting said intraocular lens in theposterior chamber of said eye.
 3. The method as defined by claim 1wherein said external lens is a negative spectacle lens.
 4. The methodas defined by claim 1 wherein said external lens is a negative contactlens.
 5. The method as defined by claim 1, wherein said demagnificationis 41%.
 6. The method as defined by claim 5, wherein said intraocularlens has a power of 40 D, and the external lens has a power of 25 D at avertex distance of 23 mm.
 7. An optical system comprising:a) anintraocular lens comprising a positive-powered section adapted to bepositioned within the posterior chamber of an eye; and b) an externallens comprising a negative-powered section whereby said intraocular lensand said external lens in combination have a power and are configured soas to provide substantial demagnification of the retinal image whileproviding an increased field of vision.
 8. The optical system as definedby claim 7, wherein said demagnification is 41%.
 9. The optical systemas defined by claim 8, wherein said intraocular lens has a power of 40D, and the external lens has a power of 25 D at a vertex distance of 23mm.